1. Field of the Invention
This invention relates to distance measuring devices and, more particularly, to a wheeled distance measuring device with an associated counter.
2. Background Art
Wheeled distance measuring devices are known in the art. It is conventional on such devices to rotatably mount a wheel on a frame that has an integral elongate handle to facilitate control thereof by an operator. The operator uses the handle to roll the wheel against a surface to be measured. As the wheel rotates, a hit pin, or the like, thereon, coacts with a counter. Each time the pin moves past the counter, it operates a lever arm, thereby recording an increment of distance. The counter has a visual display to indicate to the user the distance traversed by the wheel.
One known counter mechanism includes a lever arm which is pivotable between first and second positions and normally biased into the first position. As the wheel rotates, the hit pin engages the lever arm, effects movement of the lever arm from its first position, to its second position to thereby cause an incremental distance to be recorded on the counter, and then moves past the lever arm so that the lever arm is free to pivot under the bias force back to its first position.
The most sensitive and expensive part of the above mechanism is the counter. One problem that has plagued the art is that of the hit pin, over the course of time, inflicting damage on the counter as an incident of the wheel rotating oppositely to its intended direction for measurement. Backward rotation of the wheel causes the pin to jam against the lever arm until the rotation of the wheel is arrested by the counter. After repeated occurrences, the counter may become damaged, thereby necessitating its repair or replacement. The hit pin might also dislodge from the wheel.